1. Field of the Invention
This invention relates to digital video signal processing.
2. Description of the Prior Art
Images recorded on film or video by cameras have a characteristic degree of motion blurring associated with them due to camera integration effects, for example caused by the finite shutter-open period of a shuttered camera.
Film drama is normally acquired with a 166.degree. shutter angle at 24 frames per second, providing an integration time of 19.2 ms, whereas sports events are preferably shot with a much smaller shutter angle of, say, 30.degree., which in the case 24 frames per second gives an integration time of 3.5 ms. This allows the generally slower moving scenes in drama have a relatively smooth and fluid motion characteristic. On the other hand, for sports events, where motion may be of much higher speed, the smaller shutter angle is necessary to give adequate dynamic resolution, but the motion will look very `strobe` like. Rather than 24 frames per second, nowadays scenes are sometimes shot at a 30 Hz frame rate so as to provide better dynamic resolution and also to provide better compatibility with 60 fields per second 2:1 interlace video equipment.
One problem with the known technology is that if it is desired to use the same mechanically rotary shuttered camera for both sports-type scenes with a short integration period and drama-type scenes with a long integration period, it is necessary either to replace the shutter or to use a complex adjustable shutter.
A further problem with the known technology is that, if a mechanically rotary shuttered CCD camera is used for acquisition at 30 frames per second, it is impossible to provide an integration time as long as 9.2 ms (which is considered to be the optimum for drama-type scenes). This is because fundamental to the operation of such a camera is the requirement that the shutter angle can never be greater than 180.degree., and thus the maximum integration time is 180/(360.times.30), or 16.7 ms.